Patent GB-786403-A (GB)
Title: Negative working diazo sulfonate foils
IPC: G03C1/56
Filed: 1956-02-23
Abstract: 786,403. Photographic diazo processes. GENERAL ANILINE & FILM CORPORATION. Feb. 23, 1956 '[March 18, 1955], No. 5654/56. Class 98(2) A negative diazo sulphonate material comprises a transparent base carrying a layer of a mixture of a maleic anhydride/ vinyl compound copolymer and a compatible hydrophobic resin, the layer having been treated to make it water receptive and then imbibed with a light-sensitive diazo sulphonate and a coupling component. The vinyl compound of the copolymer may be vinyl ether such as methyl, 2- methoxyethyl, 2 - ethoxyethyl or isobutyl ether. The hydrophobic resin may be cellulose acetate, cellulose propionate, cellulose acetate propionate nitrocellulose polyvinyl acetate or polymethyl-methacrylate. The copolymer/resin mixture is applied as a solution in an organic solvent, dried and then treated with ammonia fumes or by immersion in an aqueous solution of ammonium hydroxide, 2 - amino ethanol or 2 - dimethylaminoethanol to impart watersensitivity to the layer. The layer is then treated with a sensitizing solution comprising a diazo sulphonate such as p-ethoxybenzene diazo sulphonate p-methoxybenzene diazo sulphonate or 2, 5 - dimethoxy benzene diazo sulphonate, and a coupling component such as resorcinol, phloroglucinol, 2, 2, 4, 4<SP>1</SP> - tetrahydroxybiphenyl, 4; 6 - dichlororesorcinol, 4, 4<SP>1</SP> - dihydroxybiphenyl or 1 - (5 - hydroxy - 1 - naphthyl) biguanide. The usual adjuncts employed in diazo sensitizing solutions may be added. The low density contrast of the negatives obtained may be increased by including in the material a bleachable filter layer through which the exposure is made. Thus the base may be coated on both sides with the copolymer/resin mixture, the coatings rendered water-sensitive and one layer impregnated with the diazo sulphonate-coupling component mixture while the other layer is impregnated with diazosulphonate or the diazo from a p-phenylenediamine such as the N - diethyl or N - methyl - N- butyl diamines. Alternatively the bleachable layer may be a separate one cast over the diazosulphonate layer. The materials may be used for halftone dot patterns by exposure through a contact screen. Continuous tone prints may be obtained by exposing the negative material of the invention through a silver negative, developing and printing on to a positive diazo material such as paper lacquered with cellulose acetate and sensitized with a solution containing the zinc chloride complex of N, N - diethyl - 4 - amino - 3 - ethoxybenzene diazonium chloride, 2, 3 - naphthalene diol, resorcinol and sodium 6, 7 - dihydroxynaphthalene - 3 - sulphonate. Prints of high contrast may be prepared by printing a silver negative on to a high contrast positive diazo material, printing this in turn on to the negative diazo sulphonate material of the invention and then printing this on to a positive diazo material with the sensitized surfaces in contact. Specifications 721,660 [Group VIII], 752,000 and U.S.A. reissue Specification 23,514 and U.S.A. Specifications 2,311,071, 2,478,443 and 2,478,444 are referred to.